Numerous uses of tobacco and tobacco-based products have been proposed. For example, tobacco has been smoked in pipes, cigarettes, and cigars. See e.g. Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) p. 346 (1999). More recently, there has been focus on various ways of providing various sensations of smoking, without delivering to a smoker quantities of incomplete combustion and pyrolysis products that may result from the burning of tobacco. See e.g., the background art set forth in U.S. Pat. No. 7,503,330 to Borschke et al. and U.S. Pat. No. 7,726,320 to Robinson et al., U.S. Pat. Pub. No. 2014/0261495 to Novak, III et al., and U.S. Pat. Pub. No. 2014/0096780 to Gerardi. In addition to smoking, tobacco may also be used in so-called smokeless forms. See e.g. the background art set forth in U.S. Pat. Pub. 2012/0272976 to Byrd et al. Furthermore, various materials derived and/or extracted from tobacco have been proposed to have uses in certain industrial applications. See e.g. U.S. Pat. No. 2,098,836 to Ressler; U.S. Pat. No. 2,232,662 to Hockenyos, U.S. Pat. No. 4,347,324 to Wildman et al., U.S. Pat. No. 4,289,147 to Wildman et al., U.S. Pat. Pub. Nos. 2011/01287681 to DeVall, and 2012/0260929 to Coleman et al.
Methods of extracting proteins from tobacco and tobacco components have been proposed in U.S. Pat. No. 9,301,544 to Mua et al., U.S. Pat. No. 9,175,052 to Gerardi et al., U.S. Pat. Pub. No. 2016/0192697 to Mua et al., and U.S. Pat. Pub. No. 2016/0029663 to Gerardi et al. It may be desirable to utilize protein compositions extracted from tobacco for various purposes, including the production of protein fibers. Generally, natural protein fibers (e.g. wool, silk, and the like) are well known in the textile industry. However, these animal fibers may not be abundant and may be more expensive than protein fibers from other sources. Synthetic protein fibers that are derived from soy cake and milk have been proposed, but these sources are also traditional food sources. It may be desirable to utilize other, non-food, sources for the production of protein fibers.
Ribulose-1,5-bisphosphate carboxylase/oxygenase (hereinafter “RuBisCO”) is considered the most abundant plant protein known, as it is an enzyme involved in the first major step carbon fixation by plants and other photosynthetic organisms, making it an abundant, potentially non-food protein source that may be desirable in the production of protein fibers. For example, RuBisCO may comprise up to about 25% of the total protein content of a leaf and up to about 10% of the solid matter of a leaf. Furthermore, tobacco plants may have the highest potential yield per acre of RuBisCO of all plants, without the limitation of also being a traditional food source.